VW Bug, Alternator, backwards battery - what now?

Ok,

1975 VW Beetle, carb'd, alternator.

Two students of mine hooked the battery up backwards while installing a new battery. Lots of smoke, and the "helper" just started ripping wiring out (instead of, I don't know, maybe disconnecting the battery....).

After fixing some melted wiring, we got the engine to run, but the alternator isn't giving anything. Also the "Generator" light is on when the key is off - manual says this is a pooched regulator. I mentioned it might be a fried alternator too, and we discussed the gamble about buying just a reg vs. buying a whole alt, and the risk of not being able to return the reg if it turns out the alt is baked. Student (owner) chose reg.

New reg is installed, but still no charging.

Me thinks the alternator might be hooped (diodes fried?). Zero output at all. Load test, nothing.

12V shows up at the blue wire to the regulator, and battery voltage is at the red alt output wire.

I'm not VW savvy. Where do I go from here??

There should be a procedure in the manual to check the diodes and the regulator. You'll have to open the alternator to do it and that may void the warranty.

I know less than nothing about ACVWs so keep that in mind.

Is it actually an alternator or were they still using generators?

Shawn

It is actually an alternator, which is why I pointed it out.

Still has the old Alt, just a new reg.

Dude, Rob and Dave should be your best friends if you've got an aircooled VW that needs work.

http://www.vw-resource.com/alternator_generator.html

Pretty straightforward to diagnose if you've got a meter. You have the opportunity to turn the mistake into a learning experience in troubleshooting. Mine turned out to be a fried regulator.

Best o' luck.

Since all air cooled VW's had generators, some one must have installed an alternator. Your statement " still has old alternator, just a new reg" confuses me.

iceracer wrote: Since all air cooled VW's had generators, some one must have installed an alternator. Your statement " still has old alternator, just a new reg" confuses me. Maybe the Mexican built models had alternators.

iceracer wrote:

iceracer wrote: Since all old air cooled VW's had generators, some one must have installed an alternator. Your statement " still has old alternator, just a new reg" confuses me. Maybe the Mexican built models had alternators.

how hard would it have been to take alt to store and have it tested while one was going to buy a regulator anyway?

is it an internal but replaceable regulator like fords had? i had one of those alternators test good because parts store test machine bypassed regulator, but ended up with bad regulator.

patgizz wrote: how hard would it have been to take alt to store and have it tested while one was going to buy a regulator anyway? is it an internal but replaceable regulator like fords had? i had one of those alternators test good because parts store test machine bypassed regulator, but ended up with bad regulator.

Because he's a shop teacher and his students need to learn from this.

The first car I restored was a 1967 Karmann Ghia but I remember nearly nothing about it.

We put a Porsche alternator kit in it. I seem to remember that it was internally regulated but I could be wrong.

Shawn

This won't help, but we're Canadian bugs carburated (carburetted?) in 1975? They were fuel injected here.

Thank you for the help so far.

It IS a 1975 VW Bug. Cabriolet if it matters.

It HAS a carburetor.

It HAS an alternator.

It HAS a NEW regulator installed (it installs externally) into the EXISTING alternator.

The link posted above was very informative, but I don't think it really gave me the answer to my question.

ps: iceracer - I heard you the first time

The crunch is this: there are TWO classes left in this semester, and classes will be over.

iceracer wrote: Since all air cooled VW's had generators, some one must have installed an alternator. Your statement " still has old alternator, just a new reg" confuses me.

This is not true. Air cooled VWs changed from generator to alternator with the 1973 model year. I grew up in a VW repair shop in the late 70s/early 80s.

Better than good chance that the diode is baked. Remove the alt, pull the fan and backing plate and run it down to AutoZone for testing. Get a new one there if it turns out to be bad, Easy Peasy.

Remember that you need to remove the battery plus terminal when replacing the regulator, generator, or alternator on an air cooled VW. Luck,

TC

Oh, the VW Beetles came stock with alternators from 1973 onwards.

SkinnyG wrote: Thank you for the help so far. It IS a 1975 VW Bug. Cabriolet if it matters. It HAS a carburetor. It HAS an alternator. It HAS a NEW regulator installed (it installs externally) into the EXISTING alternator. The link posted above was very informative, but I don't think it really gave me the answer to my question. ps: iceracer - I heard you the first time The crunch is this: there are TWO classes left in this semester, and classes will be over.

sorry about that triple post. Momentary brain fade.

I think you blew the diodes anyway.

The solution came to me just now..

Open your copy of "VW maintenance, Teachers Edition" and have a look in the back. The answer key should help you out.

Replace or rebuild the alternator. I did that once on one of my Type 3s, but with a generator instead. Accidentally hooked up jumper cables backwards (it was really dark) for long enough for it to shoot sparks and me yank them back off (a second maybe?). Put them back on the right way, started the car up, and the generator was toast.

M030 wrote:

iceracer wrote: Since all air cooled VW's had generators, some one must have installed an alternator. Your statement " still has old alternator, just a new reg" confuses me.

This is not true. Air cooled VWs changed from generator to alternator with the 1973 model year. I grew up in a VW repair shop in the late 70s/early 80s.

I too worked in the shop at a VW store until '76. Don't rcall any alternators.

iceracer wrote:

M030 wrote:

iceracer wrote: Since all air cooled VW's had generators, some one must have installed an alternator. Your statement " still has old alternator, just a new reg" confuses me.

This is not true. Air cooled VWs changed from generator to alternator with the 1973 model year. I grew up in a VW repair shop in the late 70s/early 80s.

I too worked in the shop at a VW store until '76. Don't rcall any alternators.

The statement is correct however, they did switch to alternators in 73

A lot has happened since '73. It is conceivable that perhaps someone may have changed something. I know, it's hard to believe....

Not all of ~us~ are completely OEM any more, either.

I'm still OEM.

Some bits have fallen off or been taken out though

JThw8 wrote:

iceracer wrote:

M030 wrote:

iceracer wrote: Since all air cooled VW's had generators, some one must have installed an alternator. Your statement " still has old alternator, just a new reg" confuses me.

This is not true. Air cooled VWs changed from generator to alternator with the 1973 model year. I grew up in a VW repair shop in the late 70s/early 80s.

I too worked in the shop at a VW store until '76. Don't rcall any alternators.

The statement is correct however, they did switch to alternators in 73

Yep, '73 was the first year for the alternator and the last year for the generator. The '73 COULD have a Bosch generator, Bosch alternator, or Motorola alternator. By '74 ('75 in the Ghias) the generator was completely phased out and they all had alternators (Bosch or Motorola).

they started using generators in 73 1/2 in the beetles pretty basic way to tell gens are bigger on the end with the pulley tha at the end by the fan shroud. if the red light is on with the car off than the regulator is shot. if its original it is stamped with a vw and has motorala stamped on it as well its located on the passenger side of the car under the back seat fastened to the side with two sheet metal screws. your not the first person to have this happen and wont be the last you should tell your students what i tell my kids "if something is hard to do than quit"......."because your not doing it right" at least with vws anyway the neg and pos terminals should be just a little different in size so you have to try harder to get that pos on the neg terminal. most people realize this when the car gives up its ghost (smoke comes out) and quickly pulls the connector of the battery. shop around online i recently found a reg for 25 bucks with the same connector as the oem reg

sorry i meant to say they started using alternators in 73 1\2

alternators are bigger around on the side with the pulley than on the side by the fan shroud....its been a long day but yeah your reg is shot if you keep this car around check out the book how to keep your volkswagen alive hy john muir i use mine frequently mine was printed in 77 but im sure you can still find one its way better than a chilton

Just a thought - when I converted my Land Rover from positive to negative earth, the procedure was something like: swap the terminals on the battery and spark the generator a couple of times. This repolarized the generator. Any chance you did this by accident?